Reciprocating motion control device

ABSTRACT

A sewing machine having a rotary drive mechanism and a needle bar mounted for reciprocation between upper and lower positions with respect to a looper includes a transmission system operably connected between the rotary drive means and the needle bar to convert the rotary motion of the drive means to reciprocating motion of the needle bar. The transmission system includes a lever pivotally mounted in the machine and pivotally connected adjacent one end to the needle bar, a crank pivotally connected at one end to the rotary drive means, and a pitman pivotally connected between the crank and the lever to convert the rotary motion of the drive means and crank to reciprocating motion for oscillating the lever and reciprocating the needle bar. The crank is operatively connected to the looper for synchronously driving the looper with the needle bar. The transmission system also includes means for selectively maintaining the line of thrust of the pitman in a first position substantially perpendicular to the lever to transmit motion thereto from the drive means for reciprocating the needle bar and in a second position substantially in alignment with the lever whereby the pitman idles under the influence of the drive means without transmitting motion to the lever or the needle bar. A gating mechanism prevents changing the line of thrust of the pitman until the needle bar is in its raised position.

finite States atent n91 McKeen [451 Apr. an, 1974 RECIPROCATING MOTION CONTROL DEVICE [75] Inventor: Leighton R. McKeen, El Paso, Tex.

[73] Assignee: Farah Manufacturing Company,

Inc., El Paso, Tex.

[22] Filed: May 31, 1972 [21] Appl. No.: 258,449

Related US. Application Data [63] Division of Ser. No. 157,842. June 29, 1971, Pat.

Primary Examiner-Samuel Scott Assistant ExaminerWe sley S. Ratliff, Jr. Attorney, Agent, or FirmCurtis, Morris & Safford [57] ABSTRACT A sewing machine having a rotary drive mechanism and a needle bar mounted for reciprocation between upper and lower positions with respect to a looper includes a transmission system operably connected between the rotary drive means and the needle bar to convert the rotary motion of the drive means to reciprocating motion of the needle bar. The transmission system includes a lever pivotally mounted in the machine and pivotally connected adjacent one end to the needle bar, a crank pivotally connected at one end to the rotary drive means, and a pitman pivotally connected between the crank and the lever to convert the rotary motion of the drive means and crank to reciprocating motion for oscillating the lever and reciprocating the needle bar. The crank is operatively connected to the looper for synchronously driving the looper with the needle bar. The transmission system also includes means for selectively maintaining the line of thrust of the pitman in a first position substantially perpendicular to the lever to transmit motion thereto from the drive means for reciprocating the needle bar and in a second position substantially in alignment with the lever whereby the pitman idles under the influence of the drive means without transmitting motion to the lever or the needle bar. A gating mechanism prevents changing the line of thrust of the pitman until the needle baris'in its raised position.

' 5 Claims, 8 Drawing Figures pmminmso @974 3.807.241

' sum 3 or 3 1 RECIPROCATING MOTION CONTROL DEVICE This is a division,'of US. Pat. application Ser. No. 157,842, filed June 29, l97l, now US. Pat. No. 3,688,715

This application is a continuationin-part of my copending US. Pat. application Ser. No. 128,831, filed Mar. 29, 1971, now U.S. Pat. No. 3,688,713 the disclosure of which is incorporated herein by reference.

This invention relates to apparatus for converting the rotary motion of a rotary drive means to reciprocating motion of a work element, and more particularly, to an apparatus for reciprocating the needle bar of a sewing machine and stopping the needle bar in a predetermined position.

In performing automatic sewing operations, particularly in industrial sewing with conventional sewing machines, it is often necessary to position the sewing needle in an up or down position with respect to the sewing surface and loo'per. The up position is required when the operator wishes to remove the work or to make necessary thread adjustments and the down position is required when the operator wishes to turn or pivot the workpiece about the engaged needle so as to permit continuedsewing in a different direction. Usually, the needle bar will not end up in the desired up or down position and'the operator, with conventional machines, is required to manually adjust the machine to raise or lower the needle bar to the desired position by turning the flywheel ofthe sewing machine. This relativelyslow manual adjustment consumes a great deal of the operators time and substantially increases the cost of the article being manufactured.

It has previously been proposed to eliminate the manual adjustment of the sewing machine by utilizing automatic or semi-automatic mechanical and electrical stop motion devices for the sewing machine. However, most of the previously proposed devices are of substantially complex construction, require extensive modifications of the sewing machine itself, and, in some cases, are suitable only for particular types of sewing machines. A number of such previously proposed devices utilize auxiliary motors and clutches to rotate the flywheel of the sewing machine to the proper position associated with the up or down position of the needle bar when the sewing machine is stopped. Other devices utilize electronic control circuits for the drive motors of the sewing machine or for engaging and disengaging pawls and cams attached to the drive shaft of the sewing machine.

While such previously proposed devices have been utilized in the field, they are relatively expensive and complicated in construction. Further, the sewing machines utilizing cams and pawls in their stop motion devices produce excessive shocks in the machine which often result in breakage, distortion and undue wear on the parts.

.In accordance with an aspect of this invention a sewing machine having a needle bar and a looper, wherein the needle bar is mounted in the machine for reciprocal movement between the upper and lower positions with respect to the looper, includes afirst lever pivotally mounted intermediate its ends and pivotally connected at one end to the needle bar for transmitting reciprocating motion thereto. rotary drive means is provided in the sewing machine along with a crank pivotally connected at one end to the rotary drive means and a pitman pivotally connected between the crank and the other end of the first lever to transmit and convert rotary motion of the drive means for reciprocating the needle bar between its upper and lower positions. A control mechanism is also provided for selectively maintaining the line of thrust of the pitman in a first position substantially perpendicular to the first lever to 'transmit motion thereto from the drive means and a second position substantially in alignment with the lever whereby the pitman idles under the influence of the drive means without transmitting motion to the lever. The control mechanism includes a second lever pivotally mounted on the machine and a hydraulic or pneumatic ram for selectively moving the second lever between the first and second positions. A control link is pivotally connected at one end to the second lever and at its other end to the crank arm at the pivotal connection between the crank arm and the pitman. The second lever and the control link cooperate to hold the pitman in either the first or second positions thereof for' selectively driving the needle bar.

In the above mentioned copending application a gate mechanism for the control system was provided in order to prevent movement of the second lever from the first to the second position thereof until the crank arm, pitman, and first lever arm achieved a relative configuration due to the rotational movement of the drive mechanism corresponding to the raised position of the needle bar so that the reciprocating motion of the needle bar would be automatically stopped with the bar in its raised position. The structure-utilized to form the gate mechanism comprised a cam plate pivotally mounted on the machine integrally with a quadrant gear engaged with a second quadrant gear secured to the second lever so that the cam plate was moved into anout of the path of travel of the point of connection between the crank arm and the pitman as the second lever moved between its first and second positions.

While this structure is extremely satisfactory in use it has been found that, in accordance with the present invention, by rigidly securing a cam plate in the machine for cooperation with a spring biased detent or cam fol-' lower located'at the pivotal connection between the crank arm and the pitman, as more fully'described hereinafter, the sewing machine may be operated at substantially greater speeds and with more efficiency. This is due, in part, to the fact thatthe mass of the gate mechanism is stationary and no longer driven. As a result, the number of sewing operations performed by a machine is increased.

' The above, and other features and advantages of this invention will be apparent in the following detailed description of an illustrative embodiment thereof which is to be read in connection with the accompanying drawings wherein:

FIG. 1 is a side elevational view, partly in section, illustrating the configuration of the transmission system of the present invention during reciprocation of the needle bar;

FIG. 1a is a partial sectional view taken along lines la1a of FIG. 1 showing the relative configuration of the transmission elements during driving of the needle bar;

FIG. 1b is an enlarged side view of the gating device or cam member used in the transmissionsystem of the invention and its cooperation with a spring detent member during reciprocation of the needle bar;

FIG. 2 is a side elevational view, similar to FIG. 1, illustrating the configiration of the transmission system when the needle bar is held in its raised position;

FIG. 2a is a partial sectional view' taken along line 2a2a of FIG. 2, showing the relative configuration of the transmission elements when the needle bar is in its at rest position;

FIG. 2b is an enlarged plan view of the gating device or cam member and its cooperation with the spring biased detent during the at rest position of the needle bar;

FIG. 3 is an exploded perspective view of the components of the device in the configuration illustrated in FIG. 1; and

FIG. 4 is a side view taken on line 44 of FIG. 2 of the cam plate utilized in the gate mechanism of the present invention.

Referring now to the drawing in detail, and initially to FIG. 1 thereof, it will be seen that a sewing machine v embodying the present invention, as shown therein, has a housing 12 which includes a rotary electric motor (notshown) that provides the power in the sewing machine to reciprocate a needle bar 16 during the sewing operation through a transmission system 18.

Themotor transmits rotary motion through a belt 19, pulley 20 and shaft 21 (FIG. 3) to a drive element 22 that is operatively connected to the transmission system 18. The latter converts the rotary motion of element 22 to reciprocating motion for moving needle bar 16 between extreme upper and lower positions with respect to a looper 24 mounted in housing 12 for cooperation with the needle 26 mounted in the needle bar.

Transmission system 18 also includes a crank arm 28 pivotally connectedat one end by a pivot pin 30 to roratingv element 22, The other-end of crank 28 is pivotally connected by pivot pin 32 to one end of an idler link'or pitman 34. The latter is utilized to transmit motion from the motor to oscillate the lever arm 36 that drives the needle bar 16. The end 38 of lever 36 is pivotally connected at 40 to pitman 34, and when the pitman is in the configuration illustrated in FIG. 1, wherein its line of thrust is substantially perpendicular to the lever, rotation of the motor causes reciprocation of pitman 34 and thus oscillation of lever 36. The end 44 of lever 36 is pivotally connected through an intermediate link 46 to needle bar 16 in order to provide a smooth reciprocating motion of the needle bar during rotation of the mtor and oscillation of lever36.

In order to maintain the line of thrust of pitman 34 substantially perpendicular to lever 36 during reciprocation of the needle bar 16, a control linkage 50 is intion of ram 60. By selectively actuating ram 60, lever 52 may be moved between first and second positions in order to vary the location of the line of thrust of pitman 34 from the position shown in FIG. 1 wherein the line of thrust is substantially perpendicular to lever 36, and the position illustrated in FIG. 2 wherein the line of thrust of the pitman is in substantial alignment with lever 36 so that'the motion of the crank arm 28 is not transmitted to lever 36 and pitman 34 merely idles about its pivotal connection 40 with that lever. This is accomplished by the utilization of a control link 64 which is pivotally connected at 66 to the end 68 of lever 52 and also is pivotally connected at its opposed end to pivot pin 32 with crank arm 28 and pitman 34.

As illustrated in FIG. 1, when the actuator rod 58 of ram 60 is extended, control link 64 cooperates with lever 52 to hold pitman 34' and thus its line of thrust substantially perpendicular to the lever 36. That is, as illustrated in dotted lines in the drawings,'as the pivot point 30 of crank 28 moves along its circular path, because of its connection with rotary drive element 22, the pivot point 32 and thus pitman 34 are held by link 64 below pivotal connection 40 and lever 36 so that the up and down movement of pivotal connection 32 is transmitted to lever 36 and causes reciprocation of needle bar 16 with respect to looper 24. Engagement of the arcuate portion 69 of lever 52 with a collar 70 or the like secured to the pivot shaft 71 of lever 36 provides a stop which limits the extent of movement of lever 52 and control rod 58 under the influence of the double acting cylinder 60, when in the position illustrated in FIG. 1.

Pitman 34 is provided with an extension 72 integral therewith which is utilized to oscillate the looper 24 in timed relation with the up and down motion of needle bar 16 for proper cooperation with needle 26. Extension 72 is pivotally connected at 74 to-a transmission link 76 that is pivotally connected at 78 to a crank arm 80. The latter is pivotally mounted in housing 12 and has a rock shaft 82 secured perpendicularly thereto. A bevel gear 84, ,is in turn, secured to shaft 82 and thus gear 84 is meshed with a corresponding bevel bear 86 that is secured to the end of a transmission shaft 88 mounted in housing 12. The end 90 of shaft 88 is secured to a looper head 92 of conventional construction. By this arrangement, it'is seen that as pitman 34 is reciprocated between its upper and lower positions,

as illustrated in solid and dotted lines in FlG.'1,' the pivot points 74 and 78 will be similarly reciprocated and crank arm will be oscillated. The oscillation of the crank'arm is transmitted by rock shaft 82 and bevel gear 84 to gear 86, thereby to effect oscillation of the transmission shaft 88 and looper 92.

When it is desired to stop reciprocation of needle bar 16, the actuator rod 58 of ram 68 is retracted, thereby moving lever 52 to the position illustrated in FIG. 2. As

a result of this motion, the control link 64 moves pivot point 32, between crank arm 28 and pitman 34, out from beneath lever 36 so that the pitman, and thus its line of thrust, is in substantial alignment with lever 36. Accordingly, as element 22 continues to rotate under the influence of motor 14, the idler link'or pitman 34 merely idles about pivot point 40 (substantially 'between the limits illustrated in solid and dotted lines in the drawing), so that needle bar l6-is not reciprocated. Since the thrust provided by pitman 34 is directed substantially longitudinally along lever-36, that lever is not oscillated. However, as pitman 34 continues to oscillate within the limits illustrated in the drawing, the extension 72 thereof also continus to oscillate and moves upwardly and downwardly with respect to pivot point 40 along'a small arc. This small oscillation is transmitted through connecting rod 76 to crank 80 to effect a slight oscillation of transmission bar 88 and looper 92. The

. continued oscillation of looper 92 is advantageous in that the looper can cooperate with a fixed knife blade adjacent the sewing surface to cut the thread on completion of the sewing operation.

When the lever 52 is moved in this manner from its first to its second position, the control link 64 is positioned in parallel to that portion of the pitman 34 between pivot points 40 and 32, with the pivotal connection 66 in alignment with pivot point 40 (see FIGS. 2 and 2a). This is permitted because the various links and levers are dimensioned so that control link 64 has a length between pivot points 32 and 66 corresponding to the distance between pivot points 32 and 40 of pitman 34. Since the location of pivot point 66 is fixed, because of its connection to the rigid lever 52, when it moves into the configuration wherein links 64 and 34 are in parallel relation, pivot point 40 becomes fixed, so that the lever arm 36 is locked in position and is prevented from oscillating.

As thus far described, the mechanism of the illustrative embodiment of the present invention is utilized in a sewing machine for reciprocating the needle bar 16 over a fixed distance or amplitude and for stopping reciprocation thereof when desired. It is noted, however,

that the control system 50 may also be used to control or vary the amplitude of oscillation of a reciprocating element such as the needle bar and in addition, may be used to control reciprocating motion in other devices such as, for example, a punch press or the agitator of a washing machine.

To control the amplitude of reciprocation of the reciprocating element, ram 60 may be provided with a conventional control device (not shown) by which the amount of retraction of actuator rod 58 may be controlled and varied. Thus, when rod 58 is fully extended, as in FIG. 1, the reciprocating member, needle 16 in the illustrative embodiment, is reciprocated at the maximum possible amplitude, i.e., it moves the maximum possible distance between its upper and lower limits. As

the rod is retracted, and before it is fully retracted, as

in FIG. 2, the pivot points 40 and 66 are moved towards each other with a scissors-like motion between members 64, 68, 36 and 34. As a result, the amplitude ofoscillation pivot point 40 and thus bar 16 is decreased. By stopping retraction of rod 58 at any point between the extremes illustrated in FIGS. 1 and 2 a desired amplitude of oscillation of'rod 16 may be selected. While this feature may be useful in sewing machines, it is particularly beneficial in numerous other reciprocating devices of applications in which the reciprocating motion control device of the present invention may be employed. Further, while rod 58 is actuated in the preferred embodiment by ram 60 it is noted that it may also be advantageously actuated and controlled by a ratchet or rack and pinion assembly or by a lead screw control device. i

The stop motion control mechanism 50 can be utilized to stop the reciprocating motion of needle bar 16 at any position of crank arm 28. When the stop motion mechanism is operated, the linkage is. moved from the position illustrated inFIG. l to theposition illustrated in FIG. 2 and the needle bar 16 is held in its raised position. However, it is preferable that the needle bar be stopped or disengaged from the material on which it is working only after the needle 26 has passed its lowermost position with respect to the looper so that the looper is engaged with the thread supplied by the needle. By this arrangement the looper holds the loop below the cloth so that when the stitch is cut, it will not ravel back, as would possibly be the case where the motion is stopped at a position wherein the loopers are withdrawn from the loop. Accordingly, a gating device is provided to insure that the stop motion actuating mechanism 50 will stop reciprocation of the needle bar 16 only after the needle 26 has moved to its lowermost position.

Gating device 100 includes agate or cam member 102 rigidly secured to the housing 12 of the sewing machine. In the illustrative embodiment the gate is integrally formed on one side 104 of a plug 106 (FIG. 4) secured in the housing. Gate 102 has an arcuate leading edge or cam surface 108 and a stepped surface 110 on the face 113 thereof. The leading edge 114 of step 110 is sloped downwardly towards surface 106 at the edge 108 for cooperation with a spring detent or cam follower 112 as more fully described hereinafter.

Cam follower 112 (see FIGS. 'la and 3) is located at pivot point 32, and is spring biased outwardly towards plug 106 and cam 102. In the first position of lever 52, pivot point 32 is kept to the left of cam 102 as seen in FIGS. 1, la and lb by the control link 64 and cam follower 112 may engage or ride along surface 108 when crank arm 28 is in the upper portions of its path of travel (seen in solid lines in FIG. 4). When it is desired to stop the machine, ram 60 is actuated to retract rod 58 and move lever 52 to the configuration of FIG. 2. To achieve this configuration, cam follower 112 must be moved to the other side of gate 102, i.e., along surface 110 (seen in dotted lines in FIG. 4). However, as seen in FIG. 1, member 112 will be trapped by surface 108 over at least a portion of its path of travel. Thus, if crank arm 28 and the pivotal connection 32 are moving upwardly on the right side of element 22, cam follower 112 would engage 108 and hold pivot point 32 and pitman 34 below point 40 so that the line of thrust of the pitman is still effective to oscillate lever 36 and lower needle bar 16. As the pivotal connection 30 of crankarm 28 with element 22 passes the top portion of its path of travel, that is, the 12 oclock position of point 30, and begins to move downwardly, cam follower 112 rides along the surface of edge 108 until it passes point 114 of the gate. As pivot point 30 continues to move downwardly, lever 36 is moved in a counterclockwise direction to raise needle bar 16, and approaches its fully raised position and follower 112 moves past point 114. When that point is passed, and bar 16 is raised, rod 58 is permitted to retract to its full extent. Simultaneously, control link 64 moves pivot point 32 from beneath pivot point 40, towards the right in FIGS. 2 and 2b, so that the line of thrust of pitman 34 is in substantial alignment with the lever. As pivot point 32 begins to move to the right, follower 112 engages rampv 114 and is depressed thereby and guided onto shoulder 110. Thereafter, as the motor continues to rotate element 22, the pivotal connection 32 will be held by control link 64 to the right of pivotal connection 40 so that the oscillating reciprocating motion of pitman 34 cannot be transmitted to the lever bar. As-a result, cam follower 112 moves along edge 110 of gate 102 as illustrated in solid and phantom lines in FIGS. 2 and 2b.

When it is desired to re-engage lever arm 36, that is, when it is desired to begin to commence sewing again and reciprocate needle bar 16, actuator rod 58 of ram 60 is extended. As actuator rod 58 is extended, link 64 tends to move pivot point 32 and thus cam follower 112, to the left in FIG. 2. However, the follower is trapped on the right of gate 102 by shoulder 110. As element 22 moves crank 28 to its lowest position, follower 112 escapes from shoulder 100. The spring (not shown) biasing the follower extends the follower as it moves down ramp 114. As a result, lever 52 is freed to return to its first position and crank 28, pitman 34 and control link 64 are returned to their positions illustrated in FIG. 1 wherein the line of thrust of the pitman is beneath lever 36 to reciprocate needle bar 16. The return to reciprocal motion of the machine can be initiated at any portion of the cycle of element 22, and actual return will occur when follower 112 is in position to escape shoulder 110.

From the foregoing description of the improvement of the present invention, it will be apparent that a relatively simple and inexpensive apparatus is provided for controlling the reciprocating motion of a needle bar and for automatically stopping the needle bar in its upthe accompanying drawing, it is to be understood that the invention is not limited to that precise embodiment and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of this invention.

What is claimed is:

l. A device for converting rotary to reciprocating motion comprising rotary drive means, a work element mounted for reciprocation between first and second positions and a transmission system operably connected between said drive means and said work element, said transmission system including a pivotally mounted lever pivotally connected to said work element, a crank pivotally connected at one end to said rotary drive means, a pitman pivotally connected between said crank and the other end of said lever to convert the rotary motion of said drive means and crank to reciprocating motion for oscillating said lever and reciprocating said work element, and means for selectively maintaining the line of thrust of said pitman in a first position substantially perpendicular to said lever to transmit motion thereto from said drive means and in a second position substantially in alignment with said lever whereby said pitman idles under the influence of and at its other end to said crank arm at the point of connection between said crank arm and said pitman, said second lever and said control link cooperating in said first position to hold the line of thrust of said pitman substantially perpendicular to the first mentioned lever and in said second position to hold the line of thrust of said pitman substantially in alignment with said first mentioned lever, and gate means including a rigidly mounted cam plate and a cam follower located at the pivotal connection between said crank and said pitman, said cam plate having a first cam surface adapted to be engaged by said cam follower to prevent movement of said second lever from said first to said second position thereof until said crank arm, pitman and first lever arm have achieved a relative configuration due to the rotational motion of said drive means corresponding substantially to the first position of said work element, said cam surface having a configuration permitting escape of said cam follower therefrom when said work element approaches its raised position whereby said second lever may be moved to its second position.

2. A device as defined in claim 1 wherein said means for moving said second lever comprises a pneumatic ram.

3. A device as defined in claim 1 wherein said cam plate includes a second cam surface angularly related to and intersecting said first cam surface to define a cam follower escape point therebetween, said second cam surface being engaged by said cam follower when said second lever is in its second position to prevent movement of said second lever from said second to said first position thereof until said cam follower is moved to a position adjacent said escape point.

4. A device as defined in claim 3 wherein said first and second cam surfaces are respectively located in spaced planes and an inclined cam transition surface is provided therebetween at said escape point.

5. A device as defined in claim 4 wherein said cam follower comprises a spring biased detent, biased towards said cam plate. 

1. A device for converting rotary to reciprocating motion comprising rotary drive means, a work element mounted for reciprocation between first and second positions and a transmission system operably connected between said drive means and said work element, said transmission system including a pivotally mounted lever pivotally connected to said work element, a crank pivotally connected at one end to said rotary drive means, a pitman pivotally connected between said crank and the other end of said lever to convert the rotary motion of said drive means and crank to reciprocating motion for oscillating said lever and reciprocating said work element, and means for selectively maintaining the line of thrust of said pitman in a first position substantially perpendicular to said lever to transmit motion thereto from said drive means and in a second position substantially in alignment with said lever whereby said pitman idles under the influence of said drive means without transmitting motion to said lever, said maintaining means including a second lever pivotally mounted in said device, means for selectively moving said second lever between first and second positions corresponding respectively to the first and second positions of said maintaining means, and a control link pivotally connected at one end to said second lever and at its other end to said crank arm at the point of connection between said crank arm and said pitman, said second lever and said control link cooperating in said first position to hold the line of thrust of said pitman substantially perpendicular to the first mentioned lever and in said second position to hold the line of thrust of said pitman substantially in alignment with said first mentioned lever, and gate means including a rigidly mounted cam plate and a cam follower located at the pivotal connection between said crank and said pitman, said cam plate having a first cam surface adapted to be engaged by said cam follower to prevent movement of said second lever from said first to said second position thereof until said crank arm, pitman and first lever arm have achieved a relative configuration due to the rotational motion of said drive means corresponding substantially to the first position of said work element, said cam surface having a configuration permitting escape of said cam follower therefrom when said work element approaches its raised position whereby said second lever may be moved to its second position.
 2. A device as defined in claim 1 wherein said means for moving said second lever comprises a pneumatic ram.
 3. A device as defined in claim 1 wherein said cam plate includes a second cam surface angularly related to and intersecting said first cam surface to define a cam follower escape point therebetween, said second cam surface being engaged by said cam follower when said second lever is in its second position to prevent movement of said second lever from said second to said first position thereof until said cam follower is moved to a position adjacent said escape point.
 4. A device as defined in claim 3 wherein said first and second cam surfaces are respectively located in spaced planes and an inclined cam transition surface is provided therebetween at said escape point.
 5. A device as defined in claim 4 wherein said cam follower comprises a spring biased detent, biased towards said cam plate. 